1. Field of the Invention
The present invention relates generally to circuit breakers, and more particularly, to a circuit breaker having a trip indicator for providing a visual indication of the trip status of the circuit breaker.
2. Description of the Related Art
Circuit breakers of the type having an electrically insulated housing, separable electrical contacts movable between closed and open positions, an operating mechanism for moving the electrical contacts between the closed and open positions, and a tripping mechanism operatively connected with the operating mechanism are generally known in the relevant art. Typically, the tripping mechanism senses an electrical condition, such as an overcurrent condition or an under-voltage condition, and actuates the operating mechanism in order to move the separable electrical contacts from the closed position to interrupt the flow of current therethrough. Inasmuch as the separable electrical contacts, operating mechanism, and tripping mechanism are typically disposed within the housing of the circuit breaker, such components typically cannot be visually inspected to determine the trip status of the circuit breaker and ascertain whether or not a tripping operation has occurred. Many circuit breakers thus are equipped with a device for indicating, either locally or at a remote location, the trip status of the circuit breaker. Such devices may take the form of mechanical and/or electrical indicators.
The trip indicator assembly disclosed generally in U.S. Pat. No. 5,886,641 to Ulerich et al. provides both mechanical and electrical indicators to indicate the trip status of a circuit breaker. The mechanical indicator thereof is in the form of an indicator end or xe2x80x9cbuttonxe2x80x9d that protrudes through a hole in a cover of a circuit breaker when the circuit breaker is in a tripped condition. The electrical indicator is provided by one or more microswitches electrically connected with bell alarms and the like, with the microswitches being operated by the same mechanical indicator that causes the xe2x80x9cbuttonxe2x80x9d to protrude from the circuit breaker cover when the circuit breaker is in the tripped condition. While the trip indicator assembly disclosed in the aforementioned patent is useful for its intended purposes, it is not, however, without limitation.
For instance, during normal operation of the circuit breaker, the button is disposed within the hole of the cover (though not protruding therefrom) and thus is subject to being vibrated by the cover during shock loading of the circuit breaker. Such vibration can have the effect of inappropriately releasing the spring-loaded button from its catch surface, whereupon the button protrudes outwardly from the cover and falsely indicates that a trip has occurred. The susceptibility of the button to inappropriately release by such vibration has numerous causes. For instance, the catch surface that is used to retain the button in the depressed condition during operation of the circuit breaker is positioned relatively closely to the cover such that even minor vibrations experienced by the cover can cause the button to disengage the catch surface and falsely indicate a tripped condition. Additionally, the catch surface resists motion of the button only with respect to a single direction, and vibrations transmitted from the cover to the button can cause movement of the button perpendicular to this direction, thus increasing the likelihood of the button becoming disengaged from the catch surface. Still further, the retention of the button on the catch surface is dependent upon the button engaging a camming surface formed on a lid that encloses the button mechanism, and any looseness of the lid with respect to the base upon which the lid sits increases the likelihood of a false trip indication and of difficulty in engaging the button with the catch surface since the button cannot properly engage the camming surface on the lid. Still further, the latch that is operated by the tripping mechanism to disengage the button from the catch surface is subject to inappropriate rotation in the presence of certain shock loading, thus further increasing the likelihood of false trip indications
It is thus desired to provide an improved indicator apparatus for a circuit breaker having a greater resistance to shock loading and having more consistent operation.
In view of the foregoing, an indicator apparatus for a circuit breaker includes an indication mechanism and a latch mechanism mounted on a base, the base being mounted within the circuit breaker. The indication mechanism includes an indicator movably mounted on the base and being translatable along a longitudinal axis between a retracted position and an extended position, with the indicator in the extended position providing an indication visible from the exterior of the circuit breaker of a tripped condition of the circuit breaker. The latch mechanism includes a latch that is moveable between a blocking position and a release position, with the latch in the blocking position being engageable with a ledge on the indicator to retain the indicator in the retracted position. The indicator is biased to the extended position by a first biasing device, and the latch is biased to the blocking position by a second biasing device.
An objective of the present invention is thus to provide an indicator apparatus for a circuit breaker that is relatively resistant to shock loading and vibration.
Another objective of the present invention is to provide an indicator apparatus for a circuit breaker that has a reduced potential for falsely indicating that the circuit breaker is in a tripped condition.
Another objective of the present invention is to provide an indicator apparatus for a circuit breaker that can be reliably manually reset.
Another objective of the present invention is to provide an indicator apparatus for a circuit breaker in which a latch is engageable with an indicator to retain the indicator in a retracted position, the latch being selectively pivotable to release the indicator and to provide an indication visible from the exterior of the circuit breaker of a tripped condition, and in which the latch is statically balanced about is pivot axis.
Another objective of the present invention is to provide a circuit breaker that includes an indication mechanism for providing an indication visible from the exterior of the circuit breaker of a tripped condition of the circuit breaker.